Process for the modification of fibrous materials



United States Patent ()fiice 2,952,580 Patented Sept. 13, 1960 PROCESSFOR THE MODIFICATION OF FIBROUS MATERIALS Herbert Manfred Freud dit JeanFrasch, 5 Boulevard du Sud-Est, Nanterre, Seine, France No Drawing.Filed Jan. 31, 1955, Ser. No. 485,313 Claims priority, applicationFrance Feb. 2, 1954 20 Claims. (Cl. 162-158) Among the com-;

to the greatest-extentin order'to'lower th'epriceof'th paper.

It should be noted that in this industry the margin of profit isextremely small and that the least reduction in expense, or economy ofmanufacture is transformed by reason of the large tonnage by which theproducts are manufactured, into considerable sums of money.

Among the other and newer type of fillers is titanium dioxide (T102)which is used despite the extremely high price thereof in order toimpart to the paper an extremely high whiteness and opacity.

The principle of action of such powdered materials such as titaniumdioxide is to fill the spaces between the fibers in such manner as to bebetter distributed by the pressure exerted by the rollers and to improvethe homogeneity of the paper. This filling of the spaces between thefibers is also of importance in the utilization of products having ahigh index of refraction such as titanium dioxide in order to improvethe opacity of the paper, the opacity being a function of the differenceof the indices of refraction between two mediums. V V

In place of having a difference of index of refraction of 0.5 betweencellulose and air (the index of refraction n for cellulose being 1.51and for air being 1) a difference in index of refraction of 1.1 isobtained in the case of utilizing titanium dioxide (n for cellulosebeing 1.51 and for titanium dioxide being 2.6).

Mainly fillers are introduced into the paper in order to obtain thehigher opacity of the fillers. But it has been found that theintroduction of a high proportion of such fillers in the paperdiminishes the mechanical properties which therefore necessitates theutilization of a thicker paper, which in itself is already more'opaque.

On the other hand it is known that because of the slight afiinity of thevarious powdered fillers for the cellulose, the retention of thesefillers by the fibers locates only about 50% of the fillers therebetweenwhich on the one hand has the effect of loss of a great part of a ratherprecious product and on the other hand has the effect of clogging theweb and scratching the rollers by reason of the particular mineralswhich are in suspension in the waters utilized in the paper industry.

It is therefore a primary object of the present invention to provide ameans for eliminating the above disadvantages of the prior art whilestill conferring to the paper a whiteness and opacity comparable topapers treated according to the known procedures but at a price which isgreatly lowered.

It is another object of the present invention to provide new productswith which paper and similar products may be treated to increase thewhiteness and opacity of the paper at substantially reduced cost.

It is still another object of the present invention to provide a methodof loading paper without the need for using powdered fillers.

It is yet another object of the present invention to provide a method offlocculating a filler material in the interior of the fiber of the paperso as to increase the whiteness andopacity thereof.

It is a further object of the present invention to provide a method oftreating paper and the like materials which not only increases thewhiteness and opacity of the paper but which does so without decreasingand in fact with increasing the mechanical strength of the paper.

, It is still afurther object of the present invention to provide amethod of increasing the whiteness and opacity of P per wh rghy at thesametime the mechanicalr strengthbfthe paper is increased and the paperis made resistant to microorganisms which are known to destroy paper.

It is yet a further object of the present invention to provide a complexcerium oxide, titanium oxide and zirconium oxide in acid solution fromwhich may be precipitated the corresponding metal compound onto orwithin the fibers of paper or the like for whitening and increasing theopacity of the paper.

The present invention also contemplates as an object thereof theproduction of relatively stable solution of cerium titanium andzirconium acid complexes.

As another object the present invention contemplates methods ofproduction of complex ceryl, titanyl and zirconyl-acidsolutionsforthe-treatment of paper and the like.

It is also an object of the present invention to provide relativelystable complex ceryl, titanyl and zirconylacid-gelatin solutions fromwhich compounds may be precipitated onto or within the fibers of paperorthe like for whitening and increasing the opacity of the paper.

The present invention also contemplates as an object thereof theproduction of relatively stable solutions of cerium, titanium and.zirconium-acid-gelatin complexes.

It is still another object of the present invention to providedispersions of powdered filler materials such as titanium dioxide in thesolutions of the present invention for the loading of paper and the liketherewith as well as with the compounds precipitated from the solutionsof the present invention.

It is a further object of the present invention to provide methods ofprecipitating the filler materials of the present invention from thesolutions of the present invention onto, between or in the fibers of thepaper or the like.

Other objects and advantages of the present invention will be apparentfrom a further reading of the specification and of theappended claims.

With the above objects in view the present invention mainly consists ina method of improving the characteristics of a fibrous celluloseproduct, comprising the steps of applying to a fibrous cellulose stockan aqueous solution having a pH -7 of at least one water-soluble complexof monovalent radical-metal oxide-organic acid radical salts, themonovalent radical being selected from the group consisting of alkalimetals and ammonium, the metal oxide being selected from the groupconsisting of ZrO TiO and CeO and the organic acid radical beingselected from the group consisting of citric acid, malic acid, tartaricacid, and lactic acid, the molecular ratio of the organic acid radicalto the metal oxide being between 1:2 and 1:6, and precipitating asubstance including the metal oxide from the applied solution while thefibrous cellulose stock is in contact therewith, whereby theprecipitated substance is retained by the fibrous cellulose stock,increasing the whiteness and opacity thereof.

According'to a preferred embodiment of the present invention thecomplexis a complex of sodium-Z1 0 citrate salts, in which case the molecularratio of citrate to ZrO is preferably between 1:2..5 and 1:4.

According to another embodiment of the present invention the complex maybe a complex of sodium-TiO citrate salts in which case the molecularratio of citrate to TiO is most preferably between 1:4.5 and 1:6. Ingeneral the solutions according to the present invention contain between26% by weight of the metal oxide, e.g. ZrO Ti0 or (3e0 although. widevariations as to the concentration of the metal oxide in the solutionare permissible, because solutions having these concentrations are easyto form and give very good results.

The solution may be applied to the fibrous cellulose stock by adding thesolution to the paper-making waters, e.g. by addition of the solution tothe beater or tub before or after the introduction of the fibrous stock.The flocculation or precipitation of the complex including the metaloxide in the paper pulp may then be accomplished by lowering the pH ofthe solution sufiiciently to cause the flocculation, preferably by theaddition of a polyvalent cation such as aluminum or thorium in the formof aluminum sulfate or thorium sulfate, for example. The exact quantityof cation necessary to cause this floccula aennepends oh' niimerousvariables such a s the initial pH of the impure waters, the quantity ofcomplex incorporated in the solution, etc. However, anyone skilled inthe art could easily determine the exact amount required forprecipitation of the complex by the polyvalent cation by simplepre-testing.

It is a great advantage of the present invention that by theprecipitation of the complex in contact with the fibrous cellulosestock, e.g. the paper pulp, what is obtained is not merely anincorporation of a mineral charge in the form of a powder in theinterstices of the paper, it actually causes a flocculation in theinterior of the fibers of thet paper of the white metal oxide such asTiO which greatly increases the opacity and the index of refraction ofthe fiber itself and therefore of the final product. This results in amuch superior increase in the whitening and opacity of the final productwith much less of the metal oxide, as will be more clearly apparent fromthe further description, then could possibly be obtained by the knownprocesses.

Additional advantageous results are obtained in ac cordance with thepresent invention, according to a preferred embodiment thereof, bydistributing the usual powdered filler, such as titanium dioxide, zincsulfide, and the like in the solution of the complex, this powderedfiller acting as adjunct to the complex in the solution and the fillerfilling the interstices between the fibers while the complex uponprecipitation thereof is embedded in the fibers themselves. However,according to this embodiment the amount of filler distributed in thesolution plus the amount of metal oxide itself in the solution in theform of a complex is always substantially less than the amount ofpowdered filler necessary according to the prior processes without theuse of the complex while achieving at least the equivalent results ofthe prior processes. This, therefore, results in a considerable thepresence of a polyvalent cation furnished by a salt l saving in thefiller material which is of great importance economically in the paperindustry.

The complexes of the present invention may be formed with an orgnaicacid containing free hydroxyl groups such as citric acid, malic acid,tartaric acid, or lactic acid. Citric acid is preferred. It should benoted, that the present invention resides in the use of relativelystable complexes as previously described which can be introduced intothe waters of the paper industry in the form of solutions and intimatelymixed with the pulp without flocculation, the flocculation resulting ina subsequent step by means of a slight variation of the pH and such asaluminum sulfate or thorium sulfate.

The simple soluble salts of titanium, zirconium, titanyl,

zirconyl such as the sulfates, chlorides and the like, cannot beutilized because they cannot be brought to a pH of 5-7 since theyalready start to flocculate at a pH of about 2.

On the other hand, certain complex radical-oxides are known in which themolecular ratio of acid radical to oxide is in the order of 2:1 to 6:1,that is, the inverse of the molecular ratios according to the presentinvention. I have determined, however, that these complexes are toostable and cannot be properly flocculated, e.g. by

means of aluminum sulfate so that it is essential according to thepresent invention that the molecular ratio of organic radical to metaloxide be within the limits specified, namely between 1:2 and 1:6.

The solutions of the complexes according to the present invention may beprepared by taking a soluble salt of zirconium, titanium or cerium suchas zirconyl sulfate or titanyl sulfate and dissolving as much aspossible thereof in water. Any concentration of the soluble salt may beutilized, but for reasons of economy it'is most suitable to utilizesaturated solutions.

To the thus-formed solution is added citric acid or an alkali metalcitrate such as sodium citrate or ammonium citrate (or tartaric. acid,malic acidior Iacticacidtorsalts thereof as the case may be) in anamount such that the ratio of citrate to the zirconium, titanium orcerium is betwen 1:2 and 1:6. In the case of zirconium, as previouslyindicated the ratio of citrate to zirconium is preferably between 1:25and 1:4 and in the case'of titanium the ratio of citrate to titanium ispreferably between 1:4.5

. thereof.

As previously indicated the solutions are introduced into the heaters orvats before or after the introduction of the paper pulp, before, afteror along with the introduction of filler materials, before or after theintroduction of resinates, but in all cases before the introduction ofthe precipitating salt such as aluminum sulfate which acts as fiocculantfor the solution which should first penetrate intimately into the fibersof the paper pulp before the flocculation is caused.

It has been found that the precipitation in the interior of the fiber inaccordance with the present invention of a hydrated oxide such as ZrOTiO or Ce0 has the effect of obtaining an opacity equivalent to thatwhich could be obtained if instead one utilized 10 to 40 times more ofthe same powder such as TiO- Zr0 or CeO- the use of the powder aloneresulting only in a clogging of the pores of the fiber.

Thus, in accordance with the invention, if utilizing a mineral fillersuch as TiO or ZnS it would be necessary to utilize 220% of the mineralfiller in relation to the and in Test B.

dry pulp, in accordance with the present invention whereby the substanceis made to precipitate in the fiber itself by the use of the solutionsof the complexes of the present invention, it is sufi'icient to utilizebetween 0.051% by weight of the weight of the dry pulp to obtain theequivalent result. It may therefore be seen that the economy in the useof the pigments which are relatively expensive in accordance with thepresent invention is highly desirable.

As also indicated previously, the use of the solutions of the complexesin accordancewith the present invention may be combined with the use ofknown filler materials in powder form in orderto increase the whitenessand opacity of paper.

The following examples will more clearly illustrate the presentinvention and .the advantages thereof as compared to the knownprocesses, the scope of the invention not, however, being limited to thespecific details of the examples.

EXAMPLE I Test A Into a heater containing 250 kg. .of dry pulp dispersedin such amount of water that the water contained 5% of pulp was added 6kg. of powdered TiO and the T10 were thoroughly mixed. The paper whichwas withdrawn had a weight of 67 g. per square meter and had thefollowing properties as measured with a refiectometer in accordance withthe I.C.I. system establishedin 1931:

Whiteness 83.25 Purity 0.64

Opacity 81.9

Test B Into a beater containing 250 kg. of dry pulp dispersed in waterin an amount such that the water contained 5% by weight of pulp wasadded 2 kg. of powdered TiO and 4 liters of the solution of the complexof sodiumzirconium-citrate prepared as above described and containing atotal of 130 g. of ZrO The pulp was-thoroughly mixed with the solutionand the powdered TiO in the beater, aluminum sulfate was then added tothe solution to cause flocculation of the ZrO, complex and the formedpaper withdrawn had a weight of 67 g. per square meter. mined as in TestA and the values were as follows:

Whiteness Purity Opacity -It=may, therefore, be seenthatthe'precipitation of 130 g. of 210 in the fibers giveidentical and evensuperior results to 4 kg. of powdered 'TiO the difference between theamount of powdered TiO used in Test A EXAMPLE II Sodium citrate wasadded to a solution of titanium sulfate dissolved in 18 liters of water,the amounts being adjusted in such manner that the solution contained 1kg. of Ti0 and so that the molecular ratio of citrate to TiO was about1:6. Sodium carbonate was then added to the solution until the pHthereof was raised to about 6.5. Upon addition of the sodium carbonate aprecipitate formed which, after a short time, redissolved by itself.

The properties of this paper was deter- The pulp The efl ectiveness ofthis solution was tested as f ollowsf Test A Into a beating troughcontaining 250 kg. of dry pulp dispersed in a sufficient amount of waterto have 5% pulp in the water was added 18 kg. of powdered TiOg. Thefinal paper product had a Weight of 44 g. per square meter and had thefollowing characteristics:

sufiicient amount of water to have 5% of pulp dispersed in the water wasadded 18 liters of the solution of the titanium complex, prepared asabove, the 18 liters containing 1 kg. of TiO The T iO was precipitatedfrom the solution by the addition of aluminum sulfate to the solution.The resulting paper had a weight of 44 g. per square meter and had thefollowing chardispersed in a acteristics:

Whiteness 87.5 Purity 0.21 Opacity 84.6

From these tests .it may be observed that the same results areobtained'when of the present-invention with only $4 of the amount ofTiO; than when using the According to the present invention, newindustrial products are produced inasmuch as the metallic oxides TiQ2t..r.O= .a.nd CeQ are-present in'or: omthe fib'e'r's of' spaces between thefibers.

the paper and not onlyin the According to another embodiment of thepresent invention, the solutions of thecomplexes invention may 'beutilized in combination with ,an albuminoid glue such as gelatin,eggwhite, lactalbumin, gluten or casein for the treatment and protectionof various products of fiber, stone or wood and, more particularly,fibrous products having a cellulose base such as papers, paper pulps,wood fibers, wood pulps, straw, textile fibers and the like. Thetreatment of such ma terials with the complex solutions described abovein combination with an albuminoid glue dissolved in the solution has theadvantage not only of increasing-the.

whiteness and opacity of the resulting product, but'also in increasingthe mechanical resistance thereof.

According to this embodiment of the presentinven tion, an albuminoidgluejis dissolvedin the solution-of invention. However, j the g; the,albuminoid glue. 7 than'lxetween 5 and 7,- and most preferably the pHshould bebetween 5.75

according to embodiment;when

the complex of the present pH of these solutions con should rather bebetween.5.5 and and 6.5.

More particularly, utilizing a complex of sodium-ZrO citrate themolecular ratio of citrate'to ZrO should be preferably between 1:2 .9 i

and 1:3.4.

The quantity of the albuminoid glue such as gelatin in the solutionshould always be less than the amount which would result in flocculationor, in other words,=- in the solution. glue containing which would causenephelometric trouble In the preparation of'the albuminoid solutionsaccording to this embodiment of the invention, the pH of the sodium-Zro-citrate solution is always adjusted to between 5.5 and 7 by theaddition of an alkali salt such as sodium carbonate before theincorporation of the albuminoid glue into the solution to preventflocculation in the solution.

The solution may be applied to the substance to be treated, e.g., paperpulp, by immersing the paper pulp in the solution, by adding thesolution to the beater or trough containing the paper pulp, by sprayingthe solution onto the paper pulp or by any other suitable method.

in order utilizing the complex solution Ti0 inthe powdered form.

of the present In the case of the paper being immersed in the solution,

it is merely necessary to removethe paper from the solution, allow it todrip, to cause retention of the complex and the albuminoid glue by thepaper.

It is known that various micro-organisms annually destroy thousands oftons of cellulose fibers, of paper and paper'pulp mainly, which rendersthe storage of these products for a prolonged period of time eitherhazardous or impractical.

In the case of paper in particular, posed-in order to provide againstthis destructionto add various antiseptic products such as borax, saltsof copper, mercury, lead, betanaphthol, etc. in the course of thepreparation of the paper or the pulp, the amount i of the antisepticbeing more or less, depending upon the particular antiseptic chosen andthe genus of mold in the particular region in which the paper is to beused. These additions generally have no effect Lon Ithequality of thepaper and on its mechanical characteristics. t

On the other hand, it is known that gelatin, the white of eggs, or othersimilar albuminoids employed in the paper industry as sizing agent forcertain quality papers, present the inconvenience of constituting anexcellent culture medium for microbes and other germs and thereforeresulting in products which are particularly fragile. The productsaccording to the present invention, on the other hand, thus have thefollowing advantages:

(1) The rendering of the paper or the fiber imputresci-- ble because theproducts according to the present invention are microbe or mushroomresistant. q 7

(2) Acting as sizing agent for the paper by reason of the presence ofthe gelatin or other analagous glue (eggwhite, fish. glue, casein orother albuminoids).

(3) Increasing the mechanical resistance of the product. I

(4) Increasing the whiteness of the product (as against results obtainedwith chromate products which have the inconvenience of yellowing theresulting product).

It is very important to note that the proportion of citrate with respectto the proportion of ZrO' (or of the other organic acid radicals to theother metallic oxides such as Ti or CeO is critical. 1

It is known that the salts of zirconium have the ability of irreversiblyflocculating gelatin. It is equally known that the alkalinization of azirconium salt suchas the acid zirconylsulfate by sodium carbonate, forexample,

leads to a flocculation of ZrO at a pH of 2.2-2.7 i'n proportion to theconcentration of the zirconium salt.

It i's-known, on the other hand, that the precipitates of ZrO or eventhe solutions" of the acid zi'rconyl sulfate are soluble in an excess ofcitric acid or of the citrate of an alkali metal or ammonia containingabout 3 molecules of citrate for 1 molecule of ZrO (which is actuallythe inverse of the molecular proportion of the present invention).However, neither the ZrO' precipitate nor the complex containing about 3molecules of citrate per each molecule of ZrO is capable of flocculatinggelatin- With the formation of a gel (the phenomenon which will hereinbe designated as the tanning of gelatin).

On the other hand, if the pH of the solution is less than 5.5, thesolution soon flocculates and is unusable, while if the pH is greaterthan 7, the solution is incapable of tanning the gelatin.

Also, itis particularly surprising that in observing the conditions ofthe present invention, and particularly the conditions of molecularratioof organic acid radical' such as citrate to metal oxide radicalsuch as ZrO and and finally dry the paper-in order.

it has been pro-- poration of is desired, the gelatin, is used in thethe pH, it is possible to obtain stable solutions, that is to say, inwhich there is neither flocculation of the ZrO nor flocculation ofgelatin, this double flocculation, however, being produced automaticallyand irreversibly (with the, formation of a gel-not of a. salt-whichapparently is constituted by a mixture of complexes of zirconium; oftannedgelatin and of various alkali salts) when't'he concentration ofthe solution is increased above a certain value as will be explainedinfurther detail.

indicated, pise'fit' iiivention, also comprises methodsof producingthe-"solutions of the present inventiemtjhemetrtodeonsisting rm(m-Fornranen of aqueous solution of a soluble salt of zirconium and ofcitric acidbr' of an alkali metal or sari er ei "'dacid and adjustingthe pH of the s lmionw-netweenss-and 7- by the addition of alkalihydroxide; carbonate-or bicarbonate; and

'-(B)1 The incorporation of gelatin or anotheralbii minoid glue intothis solution in an amount below the amount at which flocculation of thegelatin in the solution occurs.

complex formed isnot immediately soluble in the cold.

It requires a certain time, which is about five minutes,

in the case where the molecular ratio of ZrO to citrate is 3.4, to 48hours in the case where the molecular ratio of ZrO to citrate is 2.9, inorder that the resulting solution should be perfectly clear from thepoint of view of nephelomctry.

The carbonate is added either after the citrate or at the same time, ina proportion such that the pH of the final solution is between 5.5 and7, and preferably between 5175 and fijf Theproportion of the zirconium"saltin the solution is only limited bythe solubility of b the salt.

It is possible, according to the present invention, to

replace the sodium carbonate by the bicarbonate of sodium or to replacethe sodium by another alkali metal, or another salt of an alkali metalor ammonium having a pH greater than 7, the salt being used in aquantity sufiicient to neutralize the acidity of the zirconium salt andto adjust the pH of the solution to Within thevalues specified.-

According to the present invention, once the citratezirconium complexforms a perfectly clear solution, the process passes intoa secondstagethat is, the incorthe gelatin. Particularly where a whiteness formof a clear aqueous solution thereof having a pH of about 6. If the. pHof the gelatin is not between 5.5 and 7, the pH is adjusted by measuredaddition of a weak acid or a weak base.

It is not possible to add any quantities of gelatin to the solution ofthe. complex, on the contrary, the concentrations are strictly limited.As indicated, the quantity of gelatin tobe added is limited. Simpleprotesting may determine the quantity of gelatin to be added which willcause nephelometric disturbances in the solution, and after such testsit may then be determined the amount of gelatin below the amount whichwill cause the trouble, which amount is to be added to the solution.

The quantity of gelatin that may be incorporated into the definedcomplex solution varies on the one hand with the concentration of thezirconium salt of the solution, on the other hand with the quantity ofcitrate incorporated into the solution and, finally, with thedilucitrate-zirconium salt.

1n ;efie ct, it to obtain a stable solulhus, for 100 cc. of a solutioncontaining initially:

Solution ZrO; (in g.) (in g.)

too to It is Possible to Dilution with Add Gelatin in the Solution Waterbefore the Form of a 5% by Addition of Weight Solution Gelatin, Percentin the following Amounts, ml.

It may seen, from these figures, for example that the solutions 11, 25and 34 are perfectly identical from the point of view of composition inzirconium salt and citrate-that is to say, each containing 1.1% Zr0 and0.99% citrate. Nevertheless, in 100 cc. of solution 11 it is possible toadd more than 367 cc. of the 5% gelatin solution without obtaining anynephelometric trouble. In solution 25, on the other hand, thenephelometric trouble is obtained with 26.4 cc. of the 5% gelatinsolugelatin solution. It is therefore possible, according to the presentinvention, to prepare solutions containing variable quantities ofgelatin for the same concentrations of zirconium, and while alwaysobtaining satisfactory results.

It may be seen as well, from the above figures, that for a concentrationof the zirconium-citrate salt which is regularly increased byevaporation of the solvent water, for example the solutions 5, 4, 3, Q,and l, the minimum quantity of gelatin which can be tanned by 100 cc. ofthe zirconium solution diminishes with the increase of the concentrationof Zr0 from 147 to 0.1 cc., contrary to what one would predict.

Finally, the above figures show that for slight variations in thequantity of citrate added for the same quantity of ZrO as for example insolutions 2, 8, 13, and 17 where the quantities of citrate vary from1.925 and 2.1% (therefore a variation of about 8%), there is a variationin the quantity of gelatin that can be added without nephelometrictrouble from 1.1 to 147 cc.

It is therefore possible to predict the addition of greatly variablequantities of gelatin without flocculation while the complex is dilutedand with a certainty of irreversible flocculation of zirconium andtanned gelatin when a portion of the solvent water is evaporated.

It is evident that in order to preserve the solutions perfectly stable,it is necessary to add less of the gelatin than is required in order toobtain nephelometric trouble, and in general 25% of this quantity ismost usable, although the proportion may be varied between 2 and"% withgood results. If, for example, solution 5 is preparedrlhatis to. say, asolution containing 1.1% 210 and 0.96% of citrate, and if only 20 cc. of5% gelatin solution is added (1 g. of gelatin) in place of 147 cc., thesolution will remain stable.

But after having impregnated the fibers of the paper or the like andstarting the drying, When of the water are evaporated, the same resultswill occur as in the case of solution 2, that is to say, containing 3.3%ZrO and 1.99% citrate with three times the gelatin-e.g., 3 g. ofgelatin. The complex gelatin-zirconium will flocculate as soon, becausewith solution 2.1.1 cc. of' 5% it EXAMPLE III To 1 liter of a solutionof 5% of the acid sulfate of zirconium containing 22% of Zr0 at a pH of1.7 is added 52.5 cc. of asolution containing 20% of trisodium citrate,10% Na OO and 5% NaHCO The resulting pH of the solution is 6.2. Whenthis solution is titrated with a solution of 5% gelatin, it is necessaryto utilize 52.8 'cc. of the gelatin solution in order to obtain thenephelometric trouble. /3 of this quantity, that is 17.6 cc., permitsthe obtention of a stable solution conforming to the invention. Thefinal mixture contains, therefor, for 1 liter of solution, 10.3 g. ofZrO 9.8 g. of citrate and 0.82 g. of gelatin, which is about 1% Zr0 1%citrate and 0.08% gelatin.

A piece of paper having a humidity content of 50% and a whiteness byopacity of 56% was treated with this solution by soaking and drying. Theresulting paper was out in many ways. The example above given mentionsthe case of soaking. In the case of paper pulp and fibers in suspensionin water, it is sufiicient to add to the pulp or to the suspension aquantity of solution which would be calculated by relation to the paperor the fiber or other material in suspension, the active elements of thesolution having the tendency to fix themselves to the paper, fiber orother material.

' This quantity could be determined in each case as a function of theobjects to be obtained and the material to be treated. 1

According to still another embodiment of the present invention, theusual filler materials such as powdered TiO or powdered ZnS may bedispersed either in those solutions not containing the gelatin or in thegelatinoontaining solutions. i

It has been found, according to the present invention, that particularlyin the case of the gelatin-containing solutions, the powdered fillermaterial remains in stable suspension in the solution which permits theuse of lower quantities of the powdered filler and much more easilycontrollable conditions while obtaining the same results as in the knownprocesses.

According to this embodiment, the process for the treatment of the paperor pulp may proceed either by: (a) first preparing a suspension of thepowdered filler in the gelatin-zirconium complex solution andintroducing this suspension into the beater, or (b-) introducing thesolution of the gelatin-zirconium complex into the beater and thenadding the filler, the suspension-according to the presentinvention-thus being prepared in situ.

Therefore, according to this embodiment of the present invention, newindustrial products are actually produced, that is, fibrous materialssuch as paper containing ZrO (or CeO or TiO the white filler materialsuch as the powdered TiO or ZnS, and the albuminoid glue as sizing.

A series of experiments is herein reported to illustrate the propertiesor the 'gelatin z'irconiumcomplex solution on the suspensions of thewhite filler materials.

These experiments were carried-out taking powdered TiOg as the fillermaterial. In 7 identical cylinders there were prepared 7 solutionscontaining titamum oxide and the stability of these solutions wasmeasured by observing their sedimentation.

Cylinder I.This cylinder contained a suspension of 10% Ti by weight inwater. After about one minute all of the TiO fell to the bottom of thecylinder and the supernatant water was clear.

Cylinder H.This cylinder contained a suspension of 1% by weight of TiOin water. After about minutes the same phenomenon was observed as incylinder 1.

Cylinder III.This cylinder contained a suspension of 0.1% by weight ofTiO;,. The same phenomenon was observed as in the first two cylinders,but requiring 15 minutes.

Cylinder I V.-This cylinder contained a suspension of by weight of TiOin a solution containing 200 cc. per liter of the gelatin-zirconiumsolution previously described and containing 0.37% ZrO and 0.05%gelatin. After about 48 hours, only about half of the TiO,, fell to thebottom of the cylinder, the rest still remaining in suspension. Thesuspension is therefore very stable.

Cylinder V.This cylinder contained a suspension of 1% by weight of TiOin a solution containing 20 cc. per liter of the same gelatin-zirconiumcomplex solution as in cylinder IV, that is, 0.0379% ZrO and 0.005%gelatin. After about 24 hours slightly less than half of the TiO fell tothe bottom of the cylinder and the rest remained permanently insuspension.

Cylinder VI.This cylinder contained a suspension of 0.1% of TiO in asolution containing 2 cc. per liter of the same solution ofgelatin-zirconium complex as in cylinders IV and V, that is, containing0.0037% ZrO 12 and 0.0005% of gelatin. The same results were obtained asin cylinder V.

Cylinder VII.The preceding shows that very small quantities ofgelatin-Zirconium complex, that is to say, in the order of severalmilligrams per liter, added to the suspension of TiO enormouslyincreases the relative stability of the suspension.

In order to make certain that this increase of stability is not providedonly by the fact of the presence of the gelatin in the solution, thegelatin constituting by itself a dispersing agent for TiO a seventhcylinder was prepared containing a suspension of 1% of Tit); in asolution of 0.005% of gelatin (the same solution as in cylinder V butwithout any ZrO After about three hours half of the TiO fell to thebottom and in 12 hours all of the TiO; fell to the bottom, thesupernatant water had become perfectly clear.

This shows that the property of stabilizing the suspensions of the whitefillers is peculiar to the solution of the gelatin-zirconium complex.

The combination, therefore, of the gelatin-zirconium complex solutionwith dispersed powdered filler material therefore permits in the paperindustries ofavoiding practically completely any loss in the use of thefiller (losses which in the case of TiO- for example, runs to about 50%of the TiO- introduced into the heaters). therefore, results in greatlylowering the price of the final product while obtaining equal whitenmsand opacity with a. resistance increased as well as in providing amicrobial and fungicidal action as previously described.

This advantage is again illustrated by the following table giving thevalues obtained on sheets of paper prepared in heaters in thelaboratory:

These figures show that in reducing by half the quantity of T iOemployed, there is obtained by the combina-' tion of the TiO; with thezirconium-gelatin complex of the present invention unchanged qualitiesof whiteness and opacity while still increasing the tearing strength ofthe paper.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5-7 of at leastone watersoluble complex of monovalent radical-metal oxideorganic acidradical salts, said monovalent radical being selected from the groupconsisting of alkali metals and ammonium, said metal oxide beingselected from the group consisting of ZrO TiO and CeO and said organicacid radical being selected from the group consisting of citric acid,malic acid, tartaric acid and lactic aid, the molecular ratio of saidorganic acid radical to said metal oxide being between 1:2 and 1:6; andprecipitating a substance including said metal oxide from said appliedsolution while said fibrous cellulose stock is in contact therewith,whereby said precipitated substance This,

Lassa is retained by said fibrous cellulose stock, increasing thewhiteness and opacity thereof.

2. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5-7 of at leastone watersoluble complex of sodium-ZrO -citrate salts, the molecularratio of citrate to 210 being between 112.5 and 1:4, and precipitating asubstance including said ZrO from said applied solution while saidfibrous cellulose stock is in contact therewith, whereby saidprecipitated substance is retained by said fibrous cellulose stock,increasing the whiteness and opacity thereof.

3. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 57 of at leastone watersoluble complex of sodium-TiO citrate salts, the molecularratio of citrate to TiO being between 1:45 and 1:6; and precipitating asubstance including said Ti from said applied solution while saidfibrous cellulose stock is in contact therewith, whereby saidprecipitated substance is retained by said fibrous cellulose stock,increasing the whiteness and opacity thereof.

4. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having-a pH between 7 of at leastone watersoluble complex of sodium-ZrO -citrate salts, the molecularratio of citrate to ZrO being between 1:25 and 1:4, said solutioncontaining between 26% by weight of ZrO and precipitating a substanceincluding said ZrO from said applied solution while said fibrouscellulose stock is in contact therewith, Wherebysaid precipitatedsubstance is retained by said fibrous cellulose stock, increasing thewhiteness and opacity thereof.

5. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5-7 of at leastone watersoluble complex of sodium-TiO -citrate salts, the molecularratio of citrate to TiO being between 1:45 and 1:6, said solutioncontaining between 26% by weight of 'IiO ,and precipitating a substanceincluding said TiO from said applied solution while said fibrouscellulose stock is in contact therewith, whereby said precipitatedsubstance is retained by said fibrous cellulose stock, increasing thewhiteness and opacity thereof.

6. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5-7 of at leastone watersoluble complex of monovalent radical-metal oxideorganic acidradical salts, said monovalent radical being selected from the groupconsisting of alkali nietals and ammonium, said metal oxide beingselected from the group consisting of ZrO Ti0 and CeO and said or-,ganic acid radical being selected from the group consisting of citricacid, malic acid, tartaric acid and lactic acid, the molecular ratio ofsaid organic acid radical to said metal oxide being between 1:2 and 1:6,said solution having distributed therethrough at least one insolublepowdered filler; and precipitating a substance including said metaloxide from said applied solution while said fibrous cellulose stock isin contact therewith, whereby said precipitated substance and saidpowdered filler are retained by said fibrous cellulose stock, increasingthe whiteness and opacity thereof.

7. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 57 of at leastone watersoluble complex of sodium-ZrO -citrate salts, the molecularratio of citrate to ZrO being between 1:25 and 1:4, said solution havingdistributed therethrough powdered 14 TiO and precipitating a substanceincluding said ZrC from said applied solution while said fibrouscellulose stock is in contact therewith, whereby said precipitatedsubstance and said powdered TiO are retained by said fibrous cellulosestock, increasing the whiteness and opacity thereof.

8. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 57 of at leastone watersoluble complex of monovalent radical-metal oxideorganic acidradical salts, said monovalent radical being selected from the groupconsisting of alkali metals and ammonium, said metal oxide beingselected from the group consisting of ZrO TiO and CeO and said organicacid radical being selected from the group consisting of citric acid,malic acid, tartaric acid and lactic acid, the molecular ratio of saidorganic acid radical to said metal oxide being between 1:2 and 1:6; andtreating said applied solution while said fibrous cellulose stock is incontact therewith with a soluble salt of a polyvalent' metal and amineral acid in a quantity sufiicient to lower the pH of said solutionto precipitate a substance includ-' ing said metal oxide therefrom,whereby said precipitated substance is retained by said fibrouscellulose stock, increasing the whiteness and opacity thereof.

9. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5-7 of at leastone watersoluble complex of monovalent radical-metal oxideorganic acidradical salts, said monovalent radical being selected from the groupconsisting of alkali metals and ammonium, said metal oxide beingselected from' the group consisting of ZrO TiO and CeO and said organicacid radical being selected from the group consisting of citric acid,malic acid, tartaric acid and lactic acid, the molecular ratio of saidorganic acid radical to said metal oxide being between 1:2 and 1:6; andtreating said applied solution while said fibrous cellulose stock is incontact therewith with aluminum sulfate in a quantity sufiicient tolower the pH of said solution to precipitate a substance including saidmetal oxide therefrom, whereby said precipitated substance is retainedby said fibrous cellulose stock, increasing the whiteness and opacitythereof.

10. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5-7 of at leastone watersoluble complex of monovalent radical-metal oxide-or ganic acidradical salts, said monovalent being selected from the group consistingof alkali metals and ammonium, said metal oxide being selected from thegroup consistingof 'ZrO TiO and CeO and said organic acid radical beingselected from thegroup consisting of citric acid, malic acid, tartaricacid and lactic acid, the molecular ratio of said organic acid radicalto said metal oxide being between 1:2 and 1:6; and treating-said appliedsolution while said fibrous cellulose stock is in contact therewith withthorium sulfate in a quantity sufiicient to lower the pH of saidsolution to precipitate a substance including said metal oxidetherefrom, whereby said precipitated substance is retained by saidfibrous cellulose stock, increasing the whiteness and opacity thereof.

11. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5.5-7 of atleast one watersoluble complex of monovalent radical-metal oxide-organicacid radical salts, said monovalent radical being selected from thegroup consisting of alkali metals and ammonium, said metal oxide beingselected from the group consisting of ZrO ,-TiO and CeO and said organicacid radical being selected from the group consisting of citric acid,malic acid, tartaric acid and lactic acid, the molecular ratio of saidorganic acid radical to said metal oxide being between 1:2 and 1:6, saidsolution having dissolved therein an albuminoid glue in a predeterminedamount below the amount at which flocculation of said albuminoid glue insaid solution occurs; and precipitating said albuminoid glue and saidcomplex including said metal oxide from said applied solution while saidfibrous cellulose stock is in contact therewith, whereby the precipitateis retained by said fibrous cellulose stock, increasing the whitenessand opacity thereof. Y

12. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a-fibrous naturalcellulose stock an aqueous solution having a pH between 5.5-7 of atleast one watersoluble complex of monovalent radical-metal oxide-organicacid radical salts, said monovalent radical being selected from thegroup consisting of alkali metals and ammonium, said metal oxide beingselected from the group consisting of ZrO,, TiO; and :20;, and saidorganic acid radical being selected from the group consisting of citricacid, malic acid, tartaric acid and lactic acid, the molecular ratio ofsaid organic acid radical to said metal oxide being between 1:2 and 1:6,said solution having dissolved therein gelatin in a predetermined amountbelow the amount at which flocculation of said gelatin in said solutionoccursyand precipitating said gelatin and said complex including saidmetal oxide from said applied solution while said fibrous cellulosestock is in contact therewith, whereby the precipitate is retained bysaid fibrous cellulose stock, increasing the whiteness and opacitythereof.

13. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5.5 and 7 ofwater-soluble complex of sOdium-ZrO -citrate salts, the molecular ratioof citrate to Zr0 being between 1:2.9 and 1:3.4, said solution havingdissolved therein gelatin.in a predetermined amount below the amount atwhich flocculation of said gelatin in said solution occurs; andprecipitating said gelatin and said complex including said ZrO from saidapplied solution while said fibrous cellulose stock is in contacttherewith, whereby the precipitate is retained by said fibrous cellulosestock, increasing the whiteness and opacity thereof.

14. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5.75 and 6.5 ofwater-soluble complex of sodium-ZrO -citrate salts, the molecular ratioof citrate to ZrO being between 1:29 and 1:3.4, said solution havingdissolved therein gelatin in a predetermined amount below the amount atwhich flocculation of said gelatin in said solution occurs; andprecipitating said gelatin and said complex including said 210 from saidapplied solution while said fibrous cellulose stock is in contacttherewith, whereby the precipitate is retained by said fibrous cellulosestock, increasing the whiteness and opacity thereof.

15. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of spraying onto a fibrousnatural cellulose stock an aqueous solution having a pH between 5.5 and7 a water-soluble complex of sodium-ZrO -citrate salts, the molecularratio of citrate to ZrO being between 122.9 and 1:3.4, said solutionhaving dissolved therein gelatin in a predetermined amount below theamount at which flocculation of said gelatin in said solution occurs;and evaporating water from said applied solution while said fibrouscellulose stock is in contact therewith so as to precipitate saidgelatin and said complex including said ZrO from said applied solutionwhile said fibrous cellulose stock is in contact therewith, whereby theprecipitate is re- 16 tained by said fibrous celluose stock, increasingthe whiteness and opacity thereof.

16. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of immersing a fibrous naturalcellulose stock in an aqueous solution having a pH between 5.5 and 7 ofwater-soluble complex of SOdiUlIl-ZIOg-Clililifi salts, the molecularratio of citrate to ZrO being between 1:29 and 1:3.4, said solutionhaving dissolved therein gelatin in a predetermined amount below theamount at which flocculation of said gelatin in said solution occurs;and removing the thus immersed fibrous cellulose stock from saidsolution and allowing the water of said applied solution to evaporate soas to precipitate said gelatin and said complex including said ZrO fromsaid applied solution while said fibrous cellulose stock is in contacttherewith, whereby molecular ratio of citrate to Zr0 being between 112.9

and 1:3.4, said solution having dissolved therein gelatin in a'predetermined amount below the amount at which flocculation of saidgelatin in said solution occurs; and removing the thus immersed fibrouscellulose stock from said solution and allowing the water of saidapplied'solution to evaporate so as to precipitate said gelat'm and saidcomplex including said ZrO from said applied solution while said fibrouscellulose stock is in contact therewith, whereby the precipitate isretained by said fibrous cellulose stock, increasing the whiteness andopacity thereof.

18. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5.5-7 of atleast one water-soluble complex of monovalent radical-metal oxideorganicacid radical salts, said monovalent radical being selected from thegroup consisting of alkali metals and ammonium, said metal oxide beingselected from the group consisting of ZrO TiO and CeO and said organicacid radical being selected from the group consisting of citric acid,malic acid, tartaric acid and lactic acid, the molecular ratio of saidorganic acid radical to said metal oxide being between 1:2 and 1:6, saidsolution having dissolved therein an albuminoid glue in a predeterminedamount below the amount at which flocculation of said albuminoid glue insaid solution occurs, and said solution having distributed therethroughat least one insoluble powdered filler; and precipitating saidalbuminoid glue and said complex including said metal oxide from saidapplied solution while said fibrous cellulose stock is in contacttherewith, whereby the precipitate and said powdered filler are retainedby said fibrous cellulose stock, increasing the whiteness and opacitythereof.

19. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5.5-7 of awater-soluble complex of SOdium-ZrO -citrate salts, the molecular ratioof citrate to ZrO being between 1:2 and 1:6, said solution havingdissolved therein gelatin in a predetermined amount below the amount atwhich flocculation of said gelatin in said solution occurs, and saidsolution having distributed therethrough at least one insoluble powderedfiller; and precipitating said gelatin and said complex including saidZrO from said applied solution while said fibrous cellulose stock is incontact therewith, whereby the precipitate and said powdered filler areretained by said fibrous cellulose stock, increasing the whiteness andopacity thereof.

20. A method of improving the characteristics of a fibrous naturalcellulose product, comprising the steps of applying to a fibrous naturalcellulose stock an aqueous solution having a pH between 5.5-7 of awater-soluble complex of sodium-TiO -citrate salts, the molecular ratioof citrate to Ti0 being between 1:2 and 1:6, said solution havingdissolved therein gelatin in a predetermined amount below the amount atwhich flocculation of said gelatin in said solution occurs, and saidsolution having distributed therethrough at least one insoluble powderedfiller; and precipitating said gelatin and said complex including saidTiO- from said applied solution while said fibrous cellulose stock is incontact therewith, whereby the precipitate and said powdered filler areretained by said fibrous cellulose stock, increasing the whiteness andopacity thereof.

References Cited in the file of this patent UNITED STATES PATENTS1,692,372 Gardner Nov. 20, 1928

1. A METHOD OF IMPROVING THE CHARACTERISTICS OF A FIBROUS NATURALCELLULOSE PRODUCT, COMPRISING THE STEPS OF APPLYING TO A FIBROUS NATURALCELLULOSE STOCK AN AQUEOUS SOLUTION HAVING A PH-BETWEEN 5-7 OF AT LEASTONE WATERSOLUBLE COMPLEX OF MONOVALENT RADICAL-METAL OXIDEORGANIC ACIDRADICAL SALTS, SAID MONOVALENT RADICAL BEING SELECTED FROM THE GROUPCONSISTING OF ALKALI METALS AND AMMONIUM, SAID METAL OXIDE BEINGSELECTED FROM THE GROUP CONSISTING OF ZRO2, TIO2 AND CEO2 AND SAIDORGANIC ACID RADICAL BEING SELECTED FROM THE GROUP CONSISTING OF CITRICACID, MALIC ACID, TARTARIC ACID AND LACTIC AID, THE MOLECULAR RATIO OFSAID ORGANIC ACID RADICAL TO SAID METAL OXIDE BEING BETWEEN 1:2 AND 1:6,AND PRECIPITATING A SUBSTANCE INCLUDING SAID METAL OXIDE FROM SAIDAPPLIED SOLUTION WHILE SAID FIBROUS CELLULOSE STOCK IS IN CONTACTTHEREWITH, WHEREBY SAID PRECIPITATED SUBSTANCE IS RETAINED BY SAIDFIBROUS CELLULOSE STOCK, INCREASING THE WHITENESS AND OPACITY THEREOF.